package main

import (
	"embed"
	"html"
	"io/fs"
	"log/slog"
	"net/http"
	"os"
	"os/exec"
	"strings"
)

//go:embed web/*
var webFS embed.FS

func main() {
	addr := os.Getenv("LISTEN_ADDR")
	if addr == "" {
		addr = "127.0.0.1:8080"
	}

	static, err := fs.Sub(webFS, "web")
	if err != nil {
		slog.Error("embed fs", "err", err)
		os.Exit(1)
	}

	indexHTML, err := fs.ReadFile(static, "index.html")
	if err != nil {
		slog.Error("read index", "err", err)
		os.Exit(1)
	}

	mux := http.NewServeMux()
	mux.HandleFunc("GET /", func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/" {
			http.NotFound(w, r)
			return
		}
		uptime := uptimeLine()
		body := strings.ReplaceAll(string(indexHTML), "{{uptime}}", html.EscapeString(uptime))
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		w.Header().Set("Cache-Control", "no-store")
		_, _ = w.Write([]byte(body))
	})
	mux.Handle("GET /style.css", http.FileServer(http.FS(static)))

	slog.Info("listening", "addr", addr)
	if err := http.ListenAndServe(addr, mux); err != nil {
		slog.Error("serve", "err", err)
		os.Exit(1)
	}
}

func uptimeLine() string {
	out, err := exec.Command("uptime").Output()
	if err != nil {
		return "uptime unavailable"
	}
	return strings.TrimSpace(string(out))
}